A track-type mobile machine utilizes tracks located at either side of the machine to propel the machine. The tracks each include a chain having links pinned end-to-end to form a loop that extends around a drive sprocket and one or more idler wheels, and ground engaging pads connected to each pair of links in the chain. A ground engaging pad, together with a pair of links, is commonly referred to as a crawler shoe. In some embodiments, the crawler shoe is a single cast and/or forged component. Two sprockets are driven by an engine of the machine to rotate the chains of the two tracks and push the ground engaging pads against a work surface, thereby transmitting torque from the engine to the surface in opposition to a desired travel direction of the machine.
In a machine having new tracks, only a single tooth of each sprocket engages its corresponding track at any given time. This is because of spatial requirements that allow lugs of the different crawler shoes to fall between adjacent teeth of the sprocket without interference. Over time, as the tracks wear, more teeth of the sprocket engage the crawler shoe lugs until an interference occurs. When this happens, either the tracks must be replaced or larger sprockets must be installed, both of which are resource-consuming activities. Because only a single tooth of each sprocket engages the corresponding track when the track is new, excessive force can be transmitted through the single tooth into the connected crawler shoe. This excessive force can cause the sprocket and track to wear prematurely and/or to fail completely.
An alternative track arrangement is disclosed in U.S. Pat. No. 8,070,241 of Mulligan that issued on Dec. 6, 2001 (“the '241 patent”). Specifically, the '241 patent discloses an undercarriage for a work vehicle. The undercarriage includes a left-track assembly and a right-track assembly. Each of the left- and right-track assemblies has a rear dual-sprocket drive wheel that is rotatably attached to a frame of the vehicle, a font idler, upper and lower rollers, and a track trained about the drive wheel, the idler, and the rollers. The track includes a chain, and multiple ground-engaging shoes attached to the chain via bolts. Links of the chain are pivotally connected to each other by way of pins, and drive caps are mounted to opposing ends of each pin outboard of the chain links. Teeth of the dual-sprocket drive wheel engage the drive caps, thereby transmitting tractive forces through the chain to the shoes.
While the dual-sprocket arrangement of the '241 patent may be an improvement over a single-sprocket arrangement, the arrangement of the '241 patent may lack broad applicability. In particular, the dual-sprocket arrangement of the '241 patent may not be applicable to machines having integral cast or forged crawler shoes. In addition, because the teeth of the dual-sprocket drive wheel engage the drive caps at cantilevered ends of the pins and because the arrangement uses only a single chain per track assembly, the arrangement of the '241 patent may not be durable enough for large machine applications where high tractive forces are transmitted through the pins and the chain.
The disclosed track assembly is directed to overcoming one or more of the problems set forth above.